FAIRFIELD — The author of the New York Times bestseller, “American Girls,” which explores the impact of social media on teenage girls, will speak April 21 at Roger Ludlowe Middle School.

The talk by Nancy Jo Sales, co-sponsored by the Fairfield University Bookstore and the Center for Family Justice, will take place at 7 p.m. in the auditorium of the school, 698 Unquowa Road. The program will be moderated by Trevor Mullineaux, a marriage and family therapist in Southport.

Sales’ book is the product of 30 months research interviewing more than 200 teenagers across the nation, according to publicity for the book, exploring “what teenagers are doing online and, more importantly, what their life online is doing to them. It is a disturbing and often shocking narrative. Sales documents a new kind of adolescence — one dominated by frightening new social and sexual norms and with a constant digital tether.”

She reports that teen girls are often asked by males “to send nudes and racy videos ... to starting "finstas" (fake Instagram accounts) and hard-to-trace Facebook pages that bully others, to consuming and producing porn, the years of middle and high school have become both threatening and dangerous ...”

Admission to the program for one person (including one copy of the book) is $30, or $35 for two people (with a book). Part of the proceeds benefit the Center for Family Justice.

For reservations, email ckennedy7@fairifield.edu; call 203-255-7756, ext 240, or visit the bookstore at 1499 Post Road.